SUDS and Effective flood water management
Dr. Howard Robinson, head of product development at Tarmac discusses how innovative Sustainable Urban Drainage Systems (SUDS) can provide the solution to effective drainage control and water management.
The extreme flooding experienced across the UK this summer and the possibility of warmer, yet wetter winters has prompted many local authorities to look at new solutions to tackle some of the problems associated with flash flooding. Many are already implementing new Sustainable Urban Drainage Systems (SUDS) but despite the government’s encouragement, the use of SUDS is not as widespread as it could be.
Often, SUDS measures fall by the wayside – perhaps a result of cost-cutting exercises. Furthermore, there is no specific legislation to ensure that issues of sustainability are considered with regard to drainage and flood water management. Therefore the responsibility for provision, operation and maintenance of SUDS is not clearly set out. While local authorities are responsible for developing strategies to implement sustainable drainage systems, house builders and developers also need to take on the responsibility for managing flood risk. Sustainable drainage measures need to be implemented at the early stages of projects as a specific planning condition - this would provide a more robust framework for implementation.
There is however, some indication that the industry is beginning to make movements in the right direction. The Government’s Code for Sustainable Homes published last December provides incentives for house builders to adopt porous surfaces for surface water management as part of their new build programmes. New regulations also require new developments in flood risk areas to incorporate SUDS wherever possible.
Tarmac has developed a porous pavement technology which is capable of absorbing large quantities of excess surface water and at the same time remove impurities such as oil and sand from the run-off water, therefore improving its quality before it enters the environment. This porous paving system is available as an asphalt or concrete system and is capable of storing up to 40 per cent of its volume as water and is an attractive option compared to more traditional measures like ditches, catchments, ponds and swales, which sterilise development land. Another distinct advantage is that it can shorten the build programme by removing the need for conventional permanentdrainage thus providing considerable cost savings for developers and authorities alike.
Developed for light traffic areas, car parks and pedestrian footways, Tarmac's porous paving system is designed in line with the Environment Agency’s SUDS guidelines. It includes a variety of ‘green’ design features, including porous asphalt layers, an in-built weir system – which forms part of the reservoir layer providing increased storage capacity – and inlet pipes to transfer rainwater from the pavement.
An increasingly important advantage of Tarmac’s porous pavement is its cleansing effect. Once the impurities are removed from the run-off water, this filtered, cleaner water can be stored in an aggregate reservoir layer before being slowly released back into the water sewer system or by infiltration into the sub-soil. Captured grey water can also be used in applications that do not require water to be of drinking quality e.g. flushing the toilet or watering the garden. It can also be used in landscaping and water features. This can help to reduce growing demands on primary water supplies and may help to alleviate water shortages during summer periods.
For authorities with an eye on the future, another feature of the porous pavement is that once the life cycle of the porous system is complete the materials can be recycled and used in other applications.
Although there are a number of other similar SUDS systems on the market - including concrete block permeable paving (CBPP) – Tarmac’s asphalt or concrete porous pavement system has a number of important benefits over CBPP. It is less labour intensive, therefore cheaper to lay and provides a more flexible solution for technically difficult sites. It also provides a safer surface to drive on and is easier to maintain and clean. Tarmac's porous paving system has the capacity to easily accommodate a 1 in 100 year stormwater event and is designed to such a high standard that it continues to perform for many years even if the hydraulic conductivity reduces considerably due to clogging with silt and detritius entering the surface course.
Local authorities, house builders and developers clearly have a duty to accept the adoption of SUDS and take a realistic approach to incorporating them into projects. Despite the introduction of the new regulations, many would argue that there is a need for more rigorous implementation guidelines and that planning authorities need to do more to promote the sustainable use of water resources and SUDS. However, it is also the responsibility of all those in the relevant industries to continue to invest in the development of these sustainable solutions and communicate their many benefits.
20 November 2007
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